So it has come to my understanding that a little game called Ms. Pac-Man Twin finally got a dump after I had discovered the game and made mockups back in 2015 of what the game would have looked like had it been applied to more authentic hardware. I say that because the actual version takes quite a couple liberties with the source game.
To no one's surprise, it's a bootleg running off of knockoff hardware with a daughterboard slapped on, and many elements of the original game were straight up butchered or otherwise lost to SUSILU's attempts at getting a second Ms. Pac into the game.
And here we have a 16, cleanly visible from photos of a board that was sold on eBay last December. If my understanding of this is correct, then these numbers would indicate the build number associated with each board- meaning the board the current MAME dump is associated with is Board #18, the one from the eBay auction is Board #16, and the one from Robbie's coverage is any board from #01 to #09.